The present invention relates to a process for optimizing and balancing the composition of a ration feed given to a ruminant by evaluating the nutrient status of the fore-stomachs with reference to energy and protein. The invention also relates to a process to qualitatively determine the health status of a ruminant through assessment of the fore-stomach function.
The nutrient supply to a ruminant is largely dependent on the processes taking place in the rumen and reticulum. Also several diseases (for example lack of apetite, ketosis, acetonemia). mainly affecting high producing dairy cows, can be derived from a disturbed reticulo-rumen function.
Despite this we still lack simple methods which in a field situation can be of use in judging the ruminant fore-stomach (rumen-reticulum) function both in terms of nutrient supply and animal health.
The ruminant fore-stomachs contain approximately 10 milliards of bacteria and 0.1-1.0 millions of protozoa per ml rumen fluid. The fluid volume in a normal dairy cow can be 75 to 100 liters. Consequently the cow has a very numerous microbial population in the fore-stomachs which will affect the metabolism of the ration feed and also the nutrient absorbed by the animal. Roughly, the fiber degrading bacteria make up 20% of the total bacterial population while the non-fiber degrading bacteria make up 80%. Thus, there is a continuous competition for the most easily available carbohydrates in a ration feed and between these two kinds of rumen microorganisms. This will influence, among other things, the extent of fiber degradation and the production of volatile fatty acids and microbial protein.
For optimum fermentation the rumen bacteria require a suitable source of nitrogen. The fiber degrading bacteria require, among other things, ammonia for normal functions. A mixed microbial population probably also requires a certain proportion of amino acids and small peptides.
A high intake of free long-chain fatty acids has a depressing effect on rumen fiber degradation. This effect can probably be explained by a negative influence both on rumen bacteria and protozoa. Another factor of importance for the competition between different kind of bacteria and the nutrients available is the population of protozoa. The latter can fluctuate greatly, both in numbers and in composition, depending on, among other things, pH and osmolarity. In addition to a direct competition from the rumen protozoa for easily available soluble sugars they also compete indirectly by eating bacteria (predation) to a large extent.
These roughly outlined interactions between the nutrient content of the feed and the microbial population in the fore-stomachs will determine the nutrient supply to the host animal (the ruminant) and the efficiency in utilizing a given combination of feeds.
There is a strong relationship between ammonia produced in the rumen, as a result of microbial degradation of feed proteins, and the concentration of urea in plasma. Urea, a small and water soluble molecule, diffuses from the blood into i.a. the milk. The concentration in the milk fairly well reflects the concentration in the plasma. Several studies have shown that the ratio between crude protein and metabolizable energy in the ration feed is strongly related to the milk urea content. A difficulty in judging the nutrient balance in a ration feed from the milk urea content solely is that the plasma urea content, with which the milk urea content is related, arises from ammonia produced in the fore-stomachs, the caecum-colon as well as in various organs in the body. It is consequently not possible to determine from the urea content only, in milk for example, the nutrient balance in the fore-stomachs of an animal.
Milk is produced continuously by the mammary tissue and shows a day-to-day variation in urea content closely related to the urea content in plasma. A similar picture is true also for the urine. In a pooled milk sample, containing both morning and evening milk, possible diurnal variations have been even out, which can be of interest to reflect the rumen metabolism of crude protein in the feed. A single sample of milk or urine, adjusted in time to the rumen metabolism of the feed, could give a more clear picture of the activities in the fore-stomachs.
The rumen microbial mass contains a high proportion of nucleic acids. Approximately 15% of the total nitrogen content in bacteria are made up of nucleic acid nitrogen. The nucleic acids contains phosphate, sugar (ribose or deoxyribose), pyrimidines and purines. The purines are metabolised to allantoin, uric acid, hypoxanthine and xanthine in ruminants. These catabolites are excreted in the urine, in quantity in the above given order.
My research within this area has, among other things, shown the following. The excretion of allantoin in the urine of ruminants is linearly related to the flow of microbial protein to the small intestine. The endogenons (from the body) excretion of allantoin and other purine derivatives is fairly low and appears to be affected to a small extent by the animals intake of energy and protein. Previous studies have shown that nucleic acids in the feed is metabolized to a large extent in the rumen and probably leaves only a small contribution to the total flow of purine derivatives to the ruminant small intestine.
The urinary excretion of allantoin in ruminants appears to be the indicator for microbial activity in the fore-stomachs that we lack today.